Method for preparing light absorption layer of copper-indium-gallium-sulfur-selenium thin film solar cells

ABSTRACT

A preparation method of the light absorption layer of a copper-indium-gallium-sulfur-selenium film solar cell is provided. The method employs a non-vacuum liquid-phase chemical technique, which comprises following steps: forming source solution containing copper, indium, gallium, sulfur and selenium; using the solution to form a precursor film on a substrate by a non-vacuum liquid-phase process; drying and annealing the precursor film. Thus, a compound film of copper-indium-gallium-sulfur-selenium is gained.

TECHNICAL FIELD

This invention relates to the field of photovoltaic cell devices, and inparticular, mainly relates to the preparation method of light absorptionlayer of copper-indium-gallium-sulfur-selenium thin film solar cells.

BACKGROUND ART

Energy and environment issues are the two strategic problems to beaddressed for the sustainable development of human race, and it isgetting more and more important and urgent to exploit and utilize theclean and renewable energy. Solar energy is a kind of clean, abundant,locally available and renewable energy. It is of great significance toexploit and utilize solar energy. Solar cells are one of the mosteffective devices for utilizing the solar energy, among which,copper-indium-gallium-sulfur-selenium (hereafter abbreviated as CIGSS)thin film solar cells have been recognized as the most promising nextgeneration of solar cells, which represents the advantages of low-cost,high-efficient, long-term stable, superior performance under weakillumination, and desirable resistance to radiation. However, commercialmass production of CIGSS thin film solar cells has not been realizedbecause of the complicated conventional process for preparing the lightabsorption layer of CIGSS thin film solar cells, leading to a low yieldrate and a high production cost.

The methods used for preparing light absorption layer of CIGSS thin filmsolar cells can be categorized into two classes. One is the high-vacuumvapor deposition methods, such as thermal evaporation, magnetronsputtering and molecular beam epitaxy. CIGSS thin films with small areaprepared by above methods possess excellent quality, and thecorresponding solar cells can exhibit very high photoelectric conversionefficiencies. As disclosed by the US National Renewable EnergyLaboratory (NREL), a highest efficiency of 19.5% has been achieved witha copper-indium-gallium-selenium (hereafter abbreviated as CIGS) thinfilm solar cell with an effective area of 0.405 cm² prepared by theso-called three-stage co-evaporation process. However, it would bedifficult to ensure the uniformity of thin films when these methods areused for the deposition of large-area thin films. Moreover, variousfactors such as low yield rate resulted from the complexity of thoseprocesses, high capital investment, low raw material utilization rateand low productivity, leads to a very high production cost, whichprohibits the mass production of CIGSS thin film solar cells by thesemethods. The other type of method is a non-vacuum liquid phase methods.As compared with the conventional high vacuum vapor phase methods,substantial cost reduction can be achieved when using these non-vacuumliquid phase methods and large area thin films can be convenientlydeposited. Extensive and intensive researches have been conducted inrecent years as for the preparation of light absorption layer of CIGSSthin film solar cells by non-vacuum liquid phase method, which can becategorized as following:

(1) Oxide-Based Non-Vacuum Liquid Phase Method

The oxide-based non-vacuum liquid phase method comprises the followingsteps: (a) preparing of the liquid phase precursor of micro-particles ofthe oxides of copper, indium and gallium, etc., (b) coating the liquidphase precursor on substrates by various non-vacuum processes to produceprecursor films, (c) reducing the precursor films under high temperaturefollowed by selenizing them at high temperature to produce CIGS thinfilms. Kapur, etc. have reported an oxide-based non-vacuum liquid phasemethod, which was characterized in that the oxides in the liquid phaseprecursor were particulates with sub-micron size prepared by mechanicalball milling (See U.S. Pat. No. 6,127,202). In the method developed byEberspacher and Pauls, the sub-micron sized complex oxides particulateswhich were produced by the pyrolytic decomposition of liquid drop arespayed under supersonic wave onto the substrate to obtain the precursorthin film (U.S. Pat. No. 6,268,014).

Though it is quite cost efficient to prepare light absorption layers ofCIGS thin film solar cells by oxide-based non-vacuum liquid phasemethod, this method also exhibits great drawbacks. Firstly, it will be awaste of time and energy to reduce oxide-based precursor thin films inH₂ atmosphere at high temperature. Secondly, it is very hard to reducethe precursor thin films completely because of the extremely highstability of gallium oxide, which will result in a high concentration ofimpurities in the targeted CIGS thin films and poor doping of gallium.Lastly, thorough selenization of copper-indium-gallium alloy thin filmsproduced by the reduction of oxides is very hard to achieve, which isdue to the reaction kinetics mechanism.

(2) Spray Pyrolysis

It is quite cost efficient to prepare CIGSS thin films by spraypyrolysis method, however, high concentration of detrimental impurities,high roughness and un-uniformity in large area thin films hindered thepractical utilization of this method.

It is very hard to prepare CIGS thin films qualified for thephotovoltaic devices by spray pyrolysis, and solar cells prepared bythis process show extremely low photoelectric conversion efficiency,which almost excludes the industrial application of this method in CIGSthin film solar cells.

(3) Electrochemical Method

Considerable attention has been attracted to the electrochemicaldeposition of CIGS thin films ever since the first successful depositionof CuInSe₂ thin films by electrochemical method reported by Bhattacharya(J. Electrochem. Soc. 130, 2040, 1983) in 1983. A two-step depositionprocess was also developed by Bhattacharya, which is characterized inthat a copper-rich CIGS thin films were firstly deposited byelectrochemical method, followed by adding additional In, Ga and Se,etc. to the films. Thus the final composition of the targeted thin filmsis modified so as to fulfill the criterion of solar cells. A CIGS thinfilm solar cell with a photoelectric conversion efficiency of 15.4% wasfabricated employing the two-step deposition process, and it is by farthe best performed one prepared by electrochemical deposition method.

Low cost, high utilization rate of raw materials and facile depositionof large area thin films are typical advantages of electrochemicaldeposition method. However, very large gaps existing between reductionpotentials of Cu, In and Ga often bring about enrichment of copper,great difficulties in the stoichiometry control and high concentrationof impurities in the produced thin films. Subsequent modification of thestoichiometry of thin films by PVD is usually necessary, which wouldlead to a sharp increase in production cost.

(4) Non-Oxide-Based Non-Vacuum Liquid Phase Method

Non-oxide-based non-vacuum liquid phase method was developed byNanosolar corp. for preparing CIGS thin films (U.S. Pat. No. 7,306,823).This method comprises the following steps: firstly, preparingnanoparticles or quantum dots of copper or indium or gallium orselenium; secondly, coating the surface of nanoparticles or quantum dotswith one or more layers of copper, indium, gallium, and selenium, etc.wherein the stoichiometry ratios between different elements in thecoated nanoparticles are controlled by adjusting the composition andthickness of the coating layer; thirdly, dispersing the coatednanoparticles in a solvent to produce a slurry; fourthly, forming aprecursor thin film from the slurry by a non-vacuum process such asprinting, etc.; and lastly, short annealing the precursor film toproduce the targeted CIGS thin films.

Low cost, high utilization rate of raw materials, applicability offlexible substrates and facile deposition of large area thin films canbe readily achieved by this method. However, since nano-particles areused in this method, and parameters of the coated nanoparticles, such asparticle size, size distribution, surface morphology and stoichiometryare very hard to be precisely controlled, thus resulting in unfavorablecontrollability, high complexity and poor reproducibility of theprocess.

In view of above, currently available methods for producing CIGSS thinfilms exhibits defects of one kind or another, which hampers thelarge-scale commercialization of CIGS thin film solar cells. Developinga novel method for producing CIGSS thin films that can overcome abovedefects would be a great impetus, and it would be of great significanceto the industrialization of CIGS thin film solar cells.

SUMMARY OF INVENTION

The present invention is aimed to provide a novel method for producinglight absorption layers of CIGSS thin film solar cells.

For this purpose, a novel method for preparing the absorption layer ofCIGSS thin films was provided, which makes use of non-vacuum liquidphase chemical process and comprises the following steps:

(1) Forming stable source solutions of copper, indium, gallium, sulfurand selenium by dissolving chalcogenides or halides of copper, indium,gallium, and ingredients of sulfur and selenium into solvents havingstrong coordinating groups, adding a solution conditioner therein;wherein said ingredients of sulfur and selenium are selected fromelemental sulfur and selenium, amine salts or hydrazine salts of sulfurand selenium;

(2) Producing a mixed solution of copper, indium, gallium, sulfur andselenium by mixing the source solutions obtained from step (1) accordingto the stoichiometry ratios of copper, indium, gallium in the formulaCu_(1-x)In_(1-y)Ga_(y)Se_(2-z)S_(z) (0≦x≦0.3, 0≦y≦1, 0≦z≦2) of the lightabsorption layer of CIGSS thin film solar cells, together with excesssulfur and selenium;

(3) Producing precursor thin films on a substrate from the mixedsolution obtained from step (2)_by non-vacuum liquid phase process;

(4) Drying and annealing the precursor thin films obtained from step (3)to produce the targeted CIGSS compound thin films.

SUMMARY OF DRAWINGS

FIG. 1 is a process flow diagram for the preparation of the precursorsolution of CIGSS thin films;

FIG. 2 is the X-ray diffraction pattern of CIGSS powder prepared bydrying the precursor solution of CIGSS thin film at 160° C.;

FIG. 3 is the X-ray diffraction pattern of CIGSS thin film formed on aquartz substrate;

FIG. 4 is the UV-Vis transmittance spectrum of CIGSS thin film formed ona quartz substrate;

FIG. 5 is a front view and cross-sectional view scanning electronmicroscopy (SEM) image of the CIGSS thin film formed on a quartzsubstrate;

FIG. 6 is a high resolution transmission electron microscopy (HRTEM)image of CIGSS thin film;

FIG. 7 is a schematic diagram showing the structure of CIGSS thin filmsolar cell.

FIG. 8 is a schematic diagram showing the efficiency of the presentCIGSS thin film solar cell.

FIG. 9 is a schematic diagram showing the SEM image of the present CIGSSthin film solar cell.

BEST MODE FOR CARRYING OUT THE INVENTION

A great deal of experiments and investigations were conducted byinventors, and advantages can be seen apparently when employing thenovel non-vacuum solution chemical method, which can be summarized asfollows: simple in process, low cost, low capital investment, highutilization rate of raw materials, excellent controllability, highreproductivity, facile production of large-area and high-quality thinfilm as well as being favorable for large-scale production. The presentinvention is thus completed.

As used in the disclosure, the term “aryl” includes monocyclic arylscomprising six carbon atoms, bicyclic aryls containing ten carbon atomsand tricyclic aryls containing fourteen carbon atoms, wherein each cyclemay comprise 1 to 4 substituting groups. For example, the aryls includebut are not limited to phenyl, naphthyl and anthracyl.

Step 1

In Step 1 of the present invention, stable source solutions of copper,indium, gallium, sulfur and selenium are formed by dissolvingchalcogenides or halides of copper, indium, gallium as well asingredients of sulfur and selenium into solvents containing strongcoordinating groups, and adding a solution conditioner therein; whereinsaid ingredients of sulfur and selenium are selected from elementalsulfur and selenium, amine salts or hydrazine salts of sulfur andselenium, wherein

said chalcogenides of step 1 can be depicted as M₂Q, wherein M is copper(Cu), and Q is one or more chalcogens selected from sulfur (S), selenium(Se), tellurium (Te). For example, the representative chalcogenidesinclude but are not limited to Cu₂S, Cu₂Se, and Cu₂(S, Se), etc.;

said chalcogenides of step 1 can also be depicted as MQ, wherein M iscopper (Cu), and Q is one or more chalcogens selected from sulfur (S),selenium (Se), tellurium (Te). For example, the representativechalcogenides include but are not limited to CuS, CuSe, and Cu(S, Se),etc.;

said chalcogenides of step 1 can also be depicted as M′₂Q₃, wherein M′is indium (In) and/or gallium (Ga), and Q is one or more chalcogensselected from sulfur (S), selenium (Se), tellurium (Te). For example,the representative chalcogenides include but are not limited to In₂Se₃,Ga₂Se₃, (In, Ga)₂Se₃ and (In, Ga)₂(S, Se)₃, etc.;

said chalcogenides of step 1 can also be depicted as MM′Q₂, wherein M isCu, M′ is In and/or Ga, and Q is one or more chalcogens selected from S,Se, Te. For example, the representative chalcogenides include but arenot limited to CuInS₂, Cu(In, Ga)Se₂ and Cu(In, Ga)(S, Se)₂, etc.;

said halides of step 1 can be depicted as MX, wherein M is Cu, and X isone or more halogens selected from Cl, Br, I. For example, therepresentative halides include but are not limited to CuI, CuBr, andCu(Br, I), etc.;

said halides of step 1 can also be depicted as MX₂, wherein M is Cu, andX is one or more halogens selected from Cl, Br, I. For example, therepresentative halides include but are not limited to CuI₂, CuBr₂, andCu(Br, I)₂, etc.;

said halides of step 1 can also be depicted as M′X₃, wherein M′ is Inand/or Ga, and X is one or more halogens selected from Cl, Br, I. Forexample, the representative halides include but are not limited to InI₃,GaI₃, (In, Ga)I₃, and (In, Ga)(I, Br)₃, etc.;

said halides of step 1 can also be depicted as MM′X₄, wherein M is Cu,M′ is In and/or Ga, and X is one or more halogens selected from Cl, Br,I. For example, the representative halides include but are not limitedto CuInI₄, Cu(In, Ga)I₄, and Cu(In, Ga)(I, Br)₄, etc.

In Step 1, said chalcogenides and halides of copper, indium and galliumcan be used separately or in combination.

In addition, it should be pointed out that said source solutions ofcopper, indium and gallium can be prepared separately or together. Whensource solutions of different elements are separately prepared, multipleseparately-prepared source solutions can be blended such as, accordingto certain stoichiometry ratio. For example, precursor solutions ofcopper-indium and gallium can be separately prepared, followed by mixingthe two precursor solutions to form a CIGSS thin film precursor solutionwhen necessary.

In Step 1, the mixing ratio between said chalcogenides or halides of Cu,In, Ga and ingredients of sulfur and selenium can be adjusted accordingto the targeted product, that is to say, the ratio was determinedaccording to the stoichiometry ratio of Cu, In and Ga in the lightabsorption layer of CIGSS thin film solar cells,Cu_(1-x)In_(1-y)Ga_(y)Se_(2-z)S_(z) (0≦x≦0.3, 0≦y≦1, 0≦z≦2), wherein theingredients of sulfur and selenium are selected from elemental sulfurand selenium, amine salts or hydrazine salts of sulfur and selenium.

In Step 1, said solvent containing strong coordinating groups include:water (H₂O), liquid ammonia (NH₃), hydrazine compounds (R₄R₅N—NR₆R₇),lower alcohol, ethanolamine, diethanolamine, triethanolamine,isopropanolamine, formamide, N-methylformamide, N,N-dimethylformamide,acetamide, N-methylacetamide, N,N-dimethylacetamide, dimethylsulfoxide,tetrahydrothiophene-1,1-dioxide, pyrrolidone, or a mixture thereof.Preferably, the solvent having strong coordinating groups is selectedfrom the group consisting of: liquid ammonia, hydrazine compounds(R₄R₅N—NR₆R₇), diethanolamine, triethanolamine and a mixture thereof.The hydrazine compounds is represented by the formula of R₄R₅N—NR₆R₇,wherein each of R₄, R₅, R₆ and R₇ is independently selected from aryl,hydrogen, methyl, ethyl, C₃-C₆ alkyl. The lower alcohol includes:methanol, ethanol, propanol, isopropanol, butanol, isobutanol,sec-butanol, tert-butanol, pentanol, optically reactive pentanol(2-methyl-1-butanol), isopentanol, sec-pentanol, tert-pentanol and3-methyl-2-butanol or a mixture thereof. As used in this invention, saidalkyl can be linear branched alkyl. Said alkyl can also be a cyclicalkyl.

As known those skilled in the art, the solution can be stabilized byintroducing solution conditioner. The solution conditioner of step 1includes: (1) chalcogens, (2) transition elements, (3) chalcogenides ofalkali metals, (4) chalcogenides of alkali earth metals, (5) amine saltsof chalcogens, (6) alkali metals, (7) alkali earth metals. Thechalcogens are selected from the group consisting of S, Se, Te and acombination thereof; the transition elements are selected from thegroups consisting of: nickel (Ni), palladium (Pd), platinum (Pt),rhodium (Rh), iridium (Ir), ruthenium (Ru) and a combination thereof;the chalcogenides of alkali metals include A₂Q, wherein A is selectedfrom the group consisting of: Li, Na, K, Rb, Cs and a combinationthereof, and Q is selected from the group consisting of: S, Se, Te and acombination thereof; the chalcogenides of alkali earth metals includesBQ, wherein B is selected from the group consisting of: Mg, Ca, Sr, Baand a combination thereof, and Q is selected from the group consistingof: S, Se, Te and a combination thereof; the amine salts of chalcogensinclude one or a mixture of the salts formed by hydrogen sulfide (H₂S),hydrogen selenide (H₂Se) or hydrogen telluride (H₂Te) with N—R₁R₂R₃ (R₁,R₂, R₃ is independently selected from aryl, hydrogen, methyl, ethyl,C₃-C₆ alkyl), the alkali metals are selected from the group consistingof: elemental Li, Na, K, Rb and Cs, and alloys or mixtures thereof; thealkali earth metals are selected from the group consisting of elementalMg, Ca, Sr and Ba, and alloys or mixtures thereof.

It should be noted that the solution conditioner may be unnecessary ifthe source solution is adequately stable, and the amount of the solutionconditioner added to the solution is variable as long as the stabilityof the solution is ensured. This is well known to those skilled in theart.

The solution conditioner can be separated from the solution. Forexample, the solution conditioner can be separated from the solution byfiltration. It should be understood that some remaining solutionconditioners will not exert any influence on the performance of thetargeted products, which excludes the necessity of separation.

Step 2

In Step 2, the source solutions prepared in Step 1 are mixed accordingto the stoichiometry ratio of copper, indium, gallium of the lightabsorption layer of CIGSS thin film solar cell,Cu_(1-x)In_(1-y)Ga_(y)Se_(2-z)S_(z) (0≦x≦0.3, 0≦y≦1, 0≦z≦2), with excesssulfur and/or selenium to produce a mixed solution of copper, indium,gallium, sulfur and selenium.

Preferably, in the formula of Cu_(1-x)In_(1-y)Ga_(y)Se_(2-z)S_(z),0≦x≦0.3, 0.2≦y≦0.4, 0≦z≦0.2.

With regard to step 2, the excess degree of sulfur and/or selenium is0%-800%, preferably 100%-400%. The degree of excess depends on thetargeted CIGSS thin film. In another word, the relation of the sourceelements in the mixed solution of the Cu, In, Ga, S and Se, may beillustrated as in the following formula:1≦(S+Se)/M≦9, preferably, 1≦(S+Se)/M≦5,

wherein the (S+Se)/M refers to the mole ratio of the total amount of theS and Se to the total amount of the Cu, In and Ga, i.e. the (S+Se)/Mequal to 1 when the elements of the CIGSS thin film solar cell has astoichiometry mole ration.

The mole ratio of the total amount of S to the total amount of S and Sein the mixed solution of Cu, In, Ga, S and Se ranges from 0 to 1,i.e.0≦S/(S+Se)≦1, preferably, 0≦S/(S+Se)≦0.4, more preferably,0≦S/(S+Se)≦0.3.

For example, if a solution of Cu, In, Ga, S and Se contains 1 mmol S, 2mmol Se, 1 mmol Cu, 0.7 mmol In, 0.3 mmol Ga, it means that(S+Se)/M=1.5, S/(S+Se)=0.33, i.e., if the (S+Se)/M=1.5, it means thetotal amount of the S and Se is in an excess of 50%.

The present invention further provides a preferred embodiment asfollows:

providing a mixed solution of Cu, In, Ga, S and Se, wherein the moleratio of the total amount of S and Se to the total amount of Cu, In andGa ranges from 1.75 to 5, and the mole ratio of the total amount of S tothe total amount of S and Se ranges from 0 to 0.4, preferably 0 to 0.3.After continuing research, the inventor found that when the contents ofthe mixed solution of Cu, In, Ga, S and Se are refined to a certainrange, the CIGSS thin film solar cell achieved more satisfactoryperformance.

Step 3

In Step 3, the mixed solution prepared in Step 2 is applied onto asubstrate through a non-vacuum liquid phase process to produce theprecursor thin films.

Wherein said non-vacuum processes used for step 3 include: (1)spin-coating, (2) tape-casting, (3) spray-deposition, (4) dip-coating,(5) screen-printing, (6) ink-jet printing, (7) drop-casting, (8)roller-coating, (9) slot die coating, (10) Meiyerbar coating, (11)capillary coating, (12) Comma-coating, (13) gravure-coating, etc.

The substrates used for step 3 include: polyimide, Si wafer, amorphoushydrogenated silicon wafer, silicon carbide, silica, quartz, sapphire,glass, metal, diamond-like carbon, hydrogenated diamond-like carbon,gallium nitride (GaN), gallium arsenide, germanium, Si—Ge alloys, ITO,boron carbide, silicon nitride, alumina, ceria, tin oxide, zinctitanate, plastic and so on.

Step 4

In Step 4, the precursor thin films prepared in Step 3 are dried andannealed to produce the targeted CIGSS thin films.

In step 4, the procedure of drying is carried out at a temperature ofroom temperature to 80° C., though other temperature can also be adoptedas long as it is sufficient to achieve the final target.

The annealing is carried out at a temperature of 50° C. to 850° C.,preferably at a temperature of 250° C. to 650° C.

The composition of the targeted CIGSS thin film isCu_(1-x)In_(1-y)Ga_(y)Se_(2-z)S_(z), wherein 0≦x≦0.3, 0≦y≦1 and 0≦z≦2.

The thickness of the targeted CIGSS thin film can be adjusted asrequired. For example, the thickness can be 5-5000 nm, and preferably,100-3000 nm.

The present invention further provides a preferred embodiment asfollows:

the precursor thin film was annealed in Se atmosphere at a temperatureof 450-600° C. for 10 to 60 minutes, and in S atmosphere at atemperature of 350-550° C. for 10 to 60 minutes.

After continuing research, the inventor found that when precursor thinfilm is treated by particular annealing atmosphere, as a result, theCIGSS thin film solar cell achieved more satisfactory performance.

ADVANTAGES

The non-vacuum liquid phase chemical process for preparing lightabsorption layers of CIGSS thin film solar cells provided by the presentinvention exhibits the following advantages over those conventionalhigh-vacuum vapor phase methods: simple in process, low cost, favorablecontrollability, high reproductivity, production of large-area andhigh-quality thin film and favorable for large-scale production, lowcapital investment and high utilization rate of raw materials, whichleading to substantial decrease in production cost of CIGSS thin filmsolar cells, and will boosting the rapid development of CIGSS thin filmsolar cell industrialization.

Moreover, as compared with the non-vacuum liquid phase methods of theprior art, the process provided by the present invention will not behindered by the following shortcomings: incomplete selenization of theprecursor thin film occurred in the oxide-based non-vacuum liquidmethod, the complexity in the controlling of the coated nano-particlesencountered in the non-oxide-based non-vacuum liquid phase process asdeveloped by Nanosolar, the difficulties in the stoichiometry-control ofthe thin film in electrochemical deposition methods, or thehighly-concentrated impurities in the thin film prepared by spraypyrolysis.

Accurate control and continuous adjustment of the stoichiometry of thetargeted CIGSS thin film at atomic scale can be readily reached by themethod provided in this invention, and the distribution of elements canalso be facilely achieved through fabricating multi-layer thin films andadjusting the chemical composition in each layer.

The method provided by this invention is characterized by: low annealingtemperature, inhomogeneous composition in the resulted thin film, highsurface smoothness, high crystallinity, favorable orientation degree,low concentration of impurities, applicable to various substrates(including polyimide and other organic flexible substrates) and facileto control the stoichiometry and element distribution in the film, whichfacilitates the fabrication of large-area and high-quality CIGSS thinfilms. Furthermore, the utilization rate of the raw materials of Cu, In,Ga, S and Se, etc. can be up to 100%.

Other technological aspects of this invention will be apparent to thoseskilled in the art after reviewing the disclosure of the presentinvention.

Hereinafter, further description of the present invention will beprovided through specific embodiments. It should be noted that theseembodiments are merely used for explaining rather than restricting therange of the present invention. The experiment processes withoutindication of specific operational parameters in the followingembodiments are carried out under regular conditions, or follow theconditions recommended by the manufacturer. All terms of the portion andpercentage used in this invention are in weight unless otherwisespecified.

All the technical terms used in this invention are in the same meaningswith those familiar to those skilled in the relevant art unlessotherwise specified. In addition, any similar or equivalent methods ormaterials can be applied in present invention.

Example 1

1. Preparation of the precursor solution of CIGSS thin film

(a) Preparation of the solution comprising Cu and In

1 mmol Cu₂(S,Se), 0.5 mmol In₂Se₃, 0.2 mmol InI₃, 0˜8 mmol S and 0˜8mmol Se were added into 2˜16 ml mixed solvents composed of methylhydrazine, ethanolamine and dimethyl sulfoxide, wherein the volume ratiowas methyl hydrazine:ethanolamine:dimethyl sulfoxide=1˜3:1˜6:1˜8. Themixture was agitated to produce a clear solution.

(b) Preparation of the solution containing Ga

0.6 mmol Ga₂Se₃, 0.3 mmol GaBr₃, 0.1 mmol GaI₃, 0˜8 mmol Se and a traceof Ru powders were added into a 1˜8 ml mixed solvents composed of methylhydrazine, ethanolamine and dimethyl sulfoxide, wherein the volume ratiowas methyl hydrazine:ethanolamine:dimethyl sulfoxide=1˜3:1˜6:1˜8. Themixture was sufficiently agitated and filtrated through a 0.2 μm filterto produce a clear solution comprising Ga.

(c) Preparation of the precursor solution of CIGSS thin film

Above solutions comprising Cu/In and Ga are metered and blended at avolume ratio according to the stoichiometry ratios of Cu, In and Ga inthe targeted CIGSS thin film to produce the precursor solution of CIGSSthin film.

2. Preparation of CIGSS thin film

Above precursor solution of CIGSS thin film is applied onto a substratethrough a non-vacuum film-forming process (selected from spin-coating,tape-casting, stamping and printing, etc) to fabricate a precursor CIGSSthin film. After drying under low temperature (room temperature˜80° C.),the precursor CIGSS thin film was rapidly annealed under hightemperature (250° C.˜650° C.) to form CIGSS thin film.

3. Characterization of CIGSS thin film

(a) Phase characterization

The CIGSS precursor solution was dried at 120° C.˜200° C. under flow ofdried inert gas to form black powders, which was characterized by X-raydiffraction (XRD) (as shown in FIG. 2). The result showed that thepowder was CIGSS. The CIGSS thin film formed on quartz substrate wasalso characterized by XRD (as shown in FIG. 3), the XRD pattern showedthat the thin film was CIGSS will a relatively strong (112) orientation.

(b) Electrical properties

The electrical properties of the thin film were measured by afour-electrode method on Accent HL5500 Hall System. The results (asshown in Table 1) illustrated that the as-prepared CIGSS thin filmfulfilled the criterion of CIGSS thin film solar cell device.

TABLE 1 Carrier concentration Carrier mobility Sample (cm⁻³) (cm⁻² V⁻¹s⁻¹) CIGSS 1.5 × 10¹⁷ 1.12

(c) Optical properties

The UV-Vis transmittance spectrum of the CIGSS thin film formed onquartz substrate was measured. The results (as shown in FIG. 4) showedthat the band gap of the CIGS thin film could meet the requirement ofCIGS solar cell devices.

(d) Characterization of the microstructure

The microstructure of the as-formed CIGSS thin film was characterized.The left part of FIG. 5 was a front-view SEM image, and the right partwas a cross-sectional SEM image of the CIGSS thin film. The as-preparedCIGSS thin film is characterized by excellent surface smoothness,homogeneous composition and high crystallinity, as shown in FIG. 5. FIG.6 was a high resolution transmission electron microscopy (HRTEM) imageof CIGSS thin film, which further illustrated that CIGSS thin film waswell crystallized, and the lattice plane spacing is 0.331 nm, which isconsistent with the spacing between the (112) lattice planes of CIGSScrystal structure.

4. Fabrication of CIGSS thin film solar cell

The CIGSS thin film solar cell, which had a device structure as shown inFIG. 7, was prepared by a serial of steps as follows: firstly, a bufferlayer was deposited onto the CIGSS thin film to a thickness of about 50nm; then the window layer and interdigital electrode were prepared;finally, an anti-reflective film was deposited. A photoelectricconversion efficiency of 13% could be achieved with the as-fabricatedCIGSS thin film solar cell having an aperture area of 1.5 cm² afteroptimization.

Example 2

1. Preparation of the precursor solution of CIGSS thin film

(a) Preparation of the solution containing Cu

1 mmol CuI was added into 2˜16 ml ethylene glycol. The mixture wassufficiently agitated to produce a clear solution.

(b) Preparation of the solution containing In

1 mmol indium iodide and 0˜8 mmol Se were added into 1˜8 ml mixedsolvents composed of methyl hydrazine and n-butanol, wherein the volumeratio was methyl hydrazine:n-butanol=1˜3:1˜8. The mixture wassufficiently agitated and filtrated through a 0.2 μm filter to produce aclear solution containing In.

(c) Preparation of the solution containing Ga

1 mmol GaI₃ and 4˜8 mmol Se were added into 1˜8 ml mixed solventscomposed of methyl hydrazine and n-butanol, wherein the volume ratio wasmethyl hydrazinem-butanol=1˜3:1˜8. The mixture was sufficiently agitatedand filtrated through a 0.2 μm filter to produce a clear solutioncontaining Ga.

(d) Preparation of the precursor solution of CIGSS thin film

Above solutions comprising Cu, In and Ga are metered and blended at avolume ratio according to the stoichiometry ratios of Cu, In and Ga inthe targeted CIGSS thin film to produce the precursor solution of CIGSSthin film.

2. Preparation of CIGSS thin film

Above precursor solution of CIGSS thin film is applied onto a substratethrough a non-vacuum film-forming process (for example, spin-coating,tape-casting, stamping and printing, etc) to fabricate a precursor CIGSSthin film. After drying under low temperature (room temperature˜80° C.),the precursor CIGSS thin film was rapidly annealed under hightemperature (250° C.˜650° C.) to form CIGSS thin film.

3. Characterization of CIGSS thin film

(a) Phase characterization was carried out by following the proceduresof example 1 and the results were similar with that of example 1.

(b) Electric properties were characterized by following the proceduresof example 1 and the results were similar with that of example 1.

(c) Optical properties were characterized by following the procedures ofexample 1 and the results were similar with that of example 1.

(d) Microstructure was characterized by following the procedures ofexample 1 and the results were similar with that of example 1.

4. The CIGSS thin film solar cell was fabricated by following theprocedures of example 1 and the measured results were similar with thatof example 1.

Example 3

1. Preparation of the precursor solution of CIGSS thin film

(a) Preparation of the solution containing Cu and Se

1 mmol CuCl was added into 2˜16 ml mixed solvents composed of ethylenediamine, dodecyl mercaptan and N,N-dimethyl formamide, wherein volumeratio was ethylene diamine:dodecyl mercaptan:N,N-dimethylformamide=1˜8:1˜3:1˜6. The mixture was sufficiently agitated to producea clear solution containing copper. Then 2-6 mmol Se was added into 4-16ml ethylene diamine, and the mixture was sufficiently agitated andrefluxed under 80° C. to produce a clear solution of selenium inethylene diamine. The ethylene diamine solution of selenium was added inabove solution containing Cu under agitation to produce the solutioncontaining Cu and Se.

(b) Preparation of the solution containing In

1 mmol indium iodide InI₃ was added into 2˜16 ml mixed solvents composedof ethanol and isopropanol, wherein the volume ratio was ethanolisopropanol=1˜3:1˜6. The mixture was sufficiently agitated to produce aclear solution containing In.

(c) Preparation of the solution containing Ga

1 mmol GaI₃ was added into 2˜16 ml mixed solvents composed of ethanoland isopropanol, wherein the volume ratio wasethanol:isopropanol=1˜3:1˜6. The mixture was sufficiently agitated toproduce a clear solution containing Ga.

(d) Preparation of the precursor solution of CIGSS thin film

The precursor solution of CIGSS thin film was formulated by followingthe procedures of example 1.

2. Preparation of CIGSS thin film

The CIGSS thin film was prepared by following the procedures of example1.

3. Characterization of CIGSS thin film

(a) Phase characterization was carried out by following the proceduresof example 1 and the results were similar with that of example 1.

(b) Electric properties were characterized by following the proceduresof example 1 and the results were similar with that of example 1.

(c) Optical properties were characterized by following the procedures ofexample 1 and the results were similar with that of example 1.

(d) Microstructure was characterized by following the procedures ofexample 1 and the results were similar with that of example 1.

4. The CIGSS thin film solar cell device was fabricated by following theprocedures of example 1 and the measured results were similar with thatof example 1.

Example 4

1. Preparation of the precursor solution of CIGSS thin film

(a) Preparation of the solution containing Cu

1 mmol CuCl was added into 2˜16 ml mixed solvents composed of ethylenediamine, dodecyl mercaptan and N,N-dimethyl formamide, wherein volumeratio was ethylene diamine:dodecyl mercaptan:N,N-dimethylformamide=1˜8:1˜3:1˜6. The mixture was sufficiently agitated to producea clear solution containing copper. Then 2-6 mmol Se was added into 4-16ml dimethyl hydrazine, and the mixture was sufficiently agitated toproduce a clear solution of selenium in dimethyl hydrazine. The dimethylhydrazine solution of selenium was added in above solution containing Cuunder agitation to produce the solution containing Cu and Se.

(b) Preparation of the solution containing In and Ga

1 mmol (In, Ga)I₃ was added into 2˜16 ml mixed solvents composed ofethanol and isopropanol, wherein the volume ratio wasethanol:isopropanol=1˜3:1˜6. The mixture was sufficiently agitated toproduce a clear solution containing In and Ga.

(c) Preparation of the precursor solution of CIGSS thin film

The precursor solution of CIGSS thin film was formulated by followingthe procedures of example 1.

2. Preparation of CIGSS thin film

The CIGSS thin film was prepared by following the procedures of example1.

3. Characterization of CIGSS thin film

(a) Phase characterization was carried out by following the proceduresof example 1 and the results were similar with that of example 1.

(b) Electric properties were characterized by following the proceduresof example 1 and the results were similar with that of example 1.

(c) Optical properties were characterized by following the procedures ofexample 1 and the results were similar with that of example 1.

(d) Microstructure was characterized by following the procedures ofexample 1 and the results were similar with that of example 1.

4. The CIGSS thin film solar cell device was fabricated by following theprocedures of example 1 and the measured results were similar with thatof example 1.

Example 5

1. Preparation of the precursor solution of CIGSS thin film

(a) Preparation of the solution containing Cu

1 mmol CuS and 2 mmol (NH₄)₂S were added into 2˜16 ml mixed solventscomposed of triethanolamine, hydrazine hydrate and dimethyl sulfoxide,wherein volume ratio was triethanolamine:hydrazine hydrate:dimethylsulfoxide=1˜8:1˜3:1˜6. The mixture was sufficiently agitated to producea clear solution containing copper. Then 2-6 mmol Se was added into 4-16ml hydrazine hydrate, and the mixture was sufficiently agitated andrefluxed under 80° C. to produce a clear solution of selenium inhydrazine hydrate. The hydrazine hydrate solution of selenium was addedin above solution containing Cu under agitation to produce the solutioncontaining Cu and Se.

(b) Preparation of the solution containing In and Ga

1 mmol (In, Ga)I₃ was added into 2˜16 ml mixed solvents composed ofethanol and isopropanol, wherein the volume ratio wasethanol:isopropanol=1˜3:1˜6. The mixture was sufficiently agitated toproduce a clear solution containing In and Ga.

(c) Preparation of the precursor solution of CIGSS thin film

The precursor solution of CIGSS thin film was formulated by followingthe procedures of example 1.

2. Preparation of CIGSS thin film

The CIGSS thin film was prepared by following the procedures of example1.

3. Characterization of CIGSS thin film

(a) Phase characterization was carried out by following the proceduresof example 1 and the results were similar with that of example 1.

(b) Electric properties were characterized by following the proceduresof example 1 and the results were similar with that of example 1.

(c) Optical properties were characterized by following the procedures ofexample 1 and the results were similar with that of example 1.

(d) Microstructure was characterized by following the procedures ofexample 1 and the results were similar with that of example 1.

4. The CIGSS thin film solar cell device was fabricated by following theprocedures of example 1 and the measured results were similar with thatof example 1.

Example 6

1. Preparation of the precursor solution of CIGSS thin film

(a) Preparation of the solution containing Cu

1 mmol CuInSe₂ and 2 mmol (NH₄)₂S were added into 2˜16 ml mixed solventscomposed of ethylene diamine, anhydrous hydrazine and dimethylsulfoxide, wherein volume ratio was ethylene diamine:anhydroushydrazine:dimethyl sulfoxide=1˜3:1˜8:1˜6. The mixture was sufficientlyagitated under low temperature and filtered with a 0.2 μm filtrate toproduce a clear solution containing copper.

(b) Preparation of the solution containing In and Ga

1 mmol (In, Ga)₂Se₃ was added into 2˜16 ml mixed solvents composed ofethylene diamine and anhydrous hydrazine, wherein the volume ratio wasethylene diamine:anhydrous hydrazine=1˜3:1˜6. The mixture wassufficiently agitated to produce a clear solution containing In and Ga.

(c) Preparation of the precursor solution of CIGSS thin film

The precursor solution of CIGSS thin film was formulated by followingthe procedures of example 1.

2. Preparation of CIGSS thin film

The CIGSS thin film was prepared by following the procedures of example1.

3. Characterization of CIGSS thin film

(a) Phase characterization was carried out by following the proceduresof example 1 and the results were similar with that of example 1.

(b) Electric properties were characterized by following the proceduresof example 1 and the results were similar with that of example 1.

(c) Optical properties were characterized by following the procedures ofexample 1 and the results were similar with that of example 1.

(d) Microstructure was characterized by following the procedures ofexample 1 and the results were similar with that of example 1.

4. The CIGSS thin film solar cell device was fabricated by following theprocedures of example 1 and the measured results were similar with thatof example 1.

Example 7

1. Preparation of the precursor solution of CIGSS thin film

(a) Preparation of the solution containing Cu

1 mmol CuI was added into 4 ml ethanediamine, and was sufficientlyagitated under low temperature to produce a clear solution containingCu.

(b) Preparation of the solution containing In

1 mmol InI₃ was added into 4 ml methanol, and was sufficiently agitatedto produce a clear solution containing In.

(c) Preparation of the solution containing Ga

1 mmol GaI₃ was added into 4 ml methanol, and was sufficiently agitatedto produce a clear solution containing In.

(d) Preparation of the solution containing S

8 mmol S was added into 8 ml ethanediamine, and was sufficientlyagitated under low temperature to produce a clear solution containing S.

(e) Preparation of the solution containing Se

8 mmol Se was added into 16 ml ethanediamine, and was sufficientlyagitated under low temperature to produce a clear solution containingSe.

(f) Preparation of the precursor solution of CIGSS thin film

3.6 ml solution containing Cu, 2.8 ml solution containing In, 1.2 mlsolution containing Ga, 3 ml solution containing S and 0 ml solutioncontaining Se are metered and blended under a temperature of 10° C. toproduce the precursor solution of CIGSS thin film.

2. Preparation of CIGSS thin film

Firstly, drop the above precursor solution of CIGSS thin film onto aMo-coated glass and spin it at a high speed of 3000 rpm for 45 s after apre-spin of 6 s at a low speed of 1000 rpm to produce a precursor CIGSSthin film. Anneal the precursor CIGSS thin film at 300° C. for 5 min andcool it down to room temperature, thus a layer of CIGSS thin film wasgotten. Repeat the above procedure for another 9 times, and a 1.4 μmthick CIGSS thin film was fabricated. Anneal the gotten 1.4 μm thickCIGSS thin film at 550° C. for 25 min under high pure nitrogen gas (N₂),a device-quality CIGSS thin film was prepared, which can be served asthe light absorption layer of CIGSS thin film solar cell.

3. The CIGSS thin film solar cell was fabricated by following theprocedures of example 1 and a photoelectric conversion efficiency of4.97% was achieved.

Example 8

The steps of (a), (b), (c), (d), (e) in the preparation of the precursorsolution of CIGSS thin film were the same with example 7, and the stepof (f) was: 3.6 ml solution containing Cu, 2.8 ml solution containingIn, 1.2 ml solution containing Ga, 1.5 ml solution containing S and 3 mlsolution containing Se are metered and blended under a temperature of10° C. to produce the precursor solution of CIGSS thin film.

Other steps of the process were the same with example 7.

The as-fabricated CIGSS thin film solar cell has a photoelectricconversion efficiency of 7.52%.

Example 9

The steps of (a), (b), (c), (d), (e) in the preparation of the precursorsolution of CIGSS thin film were the same with example 7, and the stepof (f) was: 3.6 ml solution containing Cu, 2.8 ml solution containingIn, 1.2 ml solution containing Ga, 0.6 ml solution containing S and 4.8ml solution containing Se are metered and blended under a temperature of10° C. to produce the precursor solution of CIGSS thin film.

Other steps of the process were the same with example 7.

The as-fabricated CIGSS thin film solar cell has a photoelectricconversion efficiency of 9.4%.

Example 10

The steps of (a), (b), (c), (d), (e) in the preparation of the precursorsolution of CIGSS thin film were the same with example 7, and the stepof (f) was: 3.6 ml solution containing Cu, 2.8 ml solution containingIn, 1.2 ml solution containing Ga, 0 ml solution containing S and 6 mlsolution containing Se are metered and blended under a temperature of10° C. to produce the precursor solution of CIGSS thin film.

Other steps of the process were the same with example 7.

The as-fabricated CIGSS thin film solar cell has a photoelectricconversion efficiency of 9.1%.

Example 11

The steps of (a), (b), (c), (d), (e) in the preparation of the precursorsolution of CIGSS thin film were the same with example 7, and the stepof (f) was: 3.6 ml solution containing Cu, 2.8 ml solution containingIn, 1.2 ml solution containing Ga, 1.2 ml solution containing S and 9.6ml solution containing Se are metered and blended under a temperature of10° C. to produce the precursor solution of CIGSS thin film.

Other steps of the process were the same with example 7.

The as-fabricated CIGSS thin film solar cell has a photoelectricconversion efficiency of 13.2%.

Example 12

The steps of (a), (b), (c), (d), (e) in the preparation of the precursorsolution of CIGSS thin film were the same with example 7, and the stepof (f) was: 3.6 ml solution containing Cu, 2.8 ml solution containingIn, 1.2 ml solution containing Ga, 2 ml solution containing S and 16 mlsolution containing Se are metered and blended under a temperature of10° C. to produce the precursor solution of CIGSS thin film.

Other steps of the process were the same with example 7.

The as-fabricated CIGSS thin film solar cell has a photoelectricconversion efficiency of 10.6%.

Example 13

The steps of (a), (b), (c), (d), (e) in the preparation of the precursorsolution of CIGSS thin film were the same with example 7, and the stepof (f) was: 3.6 ml solution containing Cu, 2.8 ml solution containingIn, 1.2 ml solution containing Ga, 3.6 ml solution containing S and 28.8ml solution containing Se are metered and blended under a temperature of10° C. to produce the precursor solution of CIGSS thin film.

Other steps of the process were the same with example 7.

The as-fabricated CIGSS thin film solar cell has a photoelectricconversion efficiency of 7.4%.

Example 14

1. Preparation of the precursor solution of CIGSS thin film

(a) Preparation of the solution containing Cu

0.5 mmol Cu₂S and 1 mmol (NH₄)₂S was added into 4 ml methyl hydrazine,and sufficient ammonia gas NH₃ was introduced into the mixture, as wellas 10 μmol Na₂S was added as solution conditioner. After a sufficientstirring, a clear solution containing Cu was produced.

The steps of (b), (c), (d), (e), (f) in the preparation of the precursorsolution of CIGSS thin film were the same with example 11.

2. Preparation of CIGSS thin film

Firstly, drop the above precursor solution of CIGSS thin film onto aMo-coated glass and spin it at a high speed of 3000 rpm for 45 s after apre-spin of 6 s at a low speed of 1000 rpm to produce a precursor CIGSSthin film. Anneal the precursor CIGSS thin film at 300° C. for 5 min andcool it down to room temperature, thus a layer of CIGSS thin film wasgotten. Repeat the above procedure for another 9 times, and a 1.4 μmthick CIGSS thin film was fabricated.

3. Annealing of CIGSS thin film

Annealing the gotten 1.4 μm thick CIGSS thin film at 550° C. for 15 minunder a saturated Se atmosphere, a device-quality CIGSS thin film wasprepared, which can be served as the light absorption layer of CIGSSthin film solar cell.

4. The CIGSS thin film solar cell was fabricated by following theprocedures of example 1 and a photoelectric conversion efficiency of14.0% was achieved.

Example 15

1. The precursor solution of CIGSS thin film and the CIGSS thin filmwere fabricated by following the procedures of example 14.

2. Annealing of CIGSS thin film

Annealing the gotten 1.4 μm thick CIGSS thin film at 550° C. for 15 minunder a saturated Se atmosphere, followed by a subsequent annealing at475° C. for 25 min under a saturated S atmosphere, a device-qualityCIGSS thin film was prepared, which can be served as the lightabsorption layer of CIGSS thin film solar cell.

3. The CIGSS thin film solar cell was fabricated by following theprocedures of example 1 and a photoelectric conversion efficiency of14.6% was achieved, as illustrated in FIG. 8.

4. As illustrated in FIG. 9 is the scanning electron microscopy image ofthe as-fabricated CIGSS thin film solar cell device.

Example 16

The steps of (a) in the preparation of the precursor solution of CIGSSthin film was: 0.5 mmol Cu₂S and 1 mmol (NH₄)₂S was added into 4 mlmethyl hydrazine, and sufficient ammonia gas NH₃ was introduced into themixture, as well as 10 μmol BaS was added as solution conditioner. Aftera sufficient stirring, a clear solution containing Cu was produced.

The steps of (b), (c), (d), (e), (f) in the preparation of the precursorsolution of CIGSS thin film were the same with example 14.

Other steps of the process were the same with example 14.

The as-fabricated CIGSS thin film solar cell has a photoelectricconversion efficiency of 13.8%.

Example 17

1. The precursor solution of CIGSS thin film and the CIGSS thin filmwere fabricated by following the procedures of example 14.

2. Annealing of CIGSS thin film

Annealing the gotten 1.4 μm thick CIGSS thin film at 550° C. for 15 minunder high pure nitrogen gas (N₂), a device-quality CIGSS thin film wasprepared, which can be served as the light absorption layer of CIGSSthin film solar cell.

3. The CIGSS thin film solar cell was fabricated by following theprocedures of example 1 and a photoelectric conversion efficiency of13.4% was achieved.

The invention claimed is:
 1. A method for preparing a light absorptionlayer of copper-indium-gallium-sulfur-selenium (CIGSS) thin film solarcell, through a non-vacuum liquid phase process, the method comprisingthe steps of: (1) forming stable clear source solutions of Cu, In, Ga,S, and Se, including (a) forming stable clear source solutions of Cu bydissolving halides of Cu into a solvent selected from the groupconsisting of at least one of liquid ammonia, ethanolamine,diethanolamine, triethanolamine, isopropanolamine, formamide,N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide,N,N-dimethylacetamide, dimethylsulfoxide,tetrahydrothiophene-1,1-dioxide, pyrrolidone, and a mixture thereof, andadding a solution conditioner therein, wherein said solution conditioneris selected from the group consisting of at least one of chalcogenide ofalkali metal and chalcogenide of alkali earth metal; (b) forming stableclear source solutions of In and Ga by dissolving halides of In and Gainto a solvent selected from the group consisting of at least one ofmethanol, ethanol, propanol, isopropanol, butanol, isobutanol,sec-butanol, tert-butanol, pentanol, 2-methyl-1-butanol, isopentanol,sec-pentanol, tert-pentanol, 3-methyl-2-butanol, and a mixture thereof;and (c) forming stable clear source solutions of S and Se by dissolvingingredients of sulfur and selenium into a solvent selected from thegroup consisting of at least one of ethanolamine, diethanolamine,triethanolamine, isopropanolamine, formamide, N-methylformamide,N,N-dimethylformamide, acetamide, N-methylacetamide,N,N-dimethylacetamide, and a mixture thereof, wherein said ingredientsof sulfur and selenium are selected from the group consisting of atleast one of elemental S and Se, amine salts or hydrazine salts of S andSe; (2) producing a mixed clear solution of Cu, In, Ga, S, and Se bymixing said stable clear source solutions obtained from (1) according tothe stoichiometry ratios of Cu, In, and Ga in formulaCu_(1-x)In_(1-y)Ga_(y)Se_(2-z)S_(z) of the light absorption layer ofsaid CIGSS thin film solar cell, and excess sulfur and/or selenium,wherein 0≦x≦0.3, 0≦y≦1, 0≦z≦2, and the excess degree of S or Se is0%-800%; (3) using said mixed clear solution of (2) to form a precursorthin film on a substrate through a non-vacuum liquid phase process; and(4) drying and annealing said precursor thin film of (3) to produce aCIGSS compound thin film.
 2. The method of claim 1, wherein said halideof Cu of (1) is represented by the formula MX, wherein M is Cu, and X isone or more halogens selected from Cl, Br and I; or said halide of Cu of(1) is represented by the formula MX₂, wherein M is Cu, and X is one ormore halogens selected from Cl, Br and I; or said halide of In, Ga of(1) is represented by the formula M′X₃, wherein M′ is In and/or Ga, andX is one or more halogens selected from Cl, Br and I; or said halide ofCu, In, Ga of (1) is represented by the formula MM′X₄, wherein M is Cu,M′ is In and/or Ga, and X is one or more halogens selected from Cl, Brand I.
 3. The method of claim 1, wherein a) said amine salts of S and Seof (1) are the salts formed by H₂S and H₂Se with N—R₁R₂R₃, wherein R₁,R₂ and R₃ is independently selected from aryl, hydrogen, methyl, ethylor C₃-C₆ alkyl; or b) said hydrazine salts of S and Se of step (1) arethe salts formed by H₂S and H₂Se with R₄R₅N—NR₆R₇, wherein R₄, R₅, R₆and R₇ is independently selected from aryl, hydrogen, methyl, ethyl orC₃-C₆ alkyl.
 4. The method of claim 1, wherein said chalcogenide ofalkali metal is A₂Q, wherein A is selected from the group consisting ofLi, Na, K, Rb, Cs and a combination thereof, and Q is selected from thegroup consisting of S, Se, Te and a combination thereof; and saidchalcogenide of alkali earth metal is BQ, wherein B is selected from thegroup consisting of Mg, Ca, Sr, Ba and a combination thereof, and Q isselected from the group consisting of S, Se, Te and a combinationthereof.
 5. The method of claim 1, wherein said excess degree of S or Seis 100%-400%.
 6. The method of claim 1, wherein, a mole ratio of a totalamount of S and Se to a total amount of Cu, In and Ga ranges from 1.75to 5 in said mixed clear solution of Cu, In, Ga, S and Se of step (2),and a mole ratio of a total amount of S to a total amount of S and Seranges from 0 to 0.4 in said mixed clear solution of Cu, In, Ga, S andSe of step (2).
 7. The method of claim 1, wherein said light absorptionlayer of CIGSS thin film solar cell of (2) has a formulaCu_(1-x)In_(1-y)Ga_(y)Se_(2-z)S_(z), wherein 0≦x≦0.3, 0.2≦y≦0.4,0≦z≦0.2.
 8. The method of claim 1, wherein said non-vacuum liquid phaseprocess, which is used in step (3) for preparing said precursor thinfilm, is selected from the group consisting of spin-coating,tape-casting, spray-deposition, dip-coating, screen-printing, ink-jetprinting, drop-casting, roller-coating, slot die coating, Meiyerbarcoating, capillary coating, Comma-coating or gravure-coating; or saidsubstrate of (3) is selected from any of the group consisting ofpolyimide, Si wafer, amorphous hydrogenated silicon wafer, siliconcarbide, silica, quartz, sapphire, glass, metal, diamond-like carbon,hydrogenated diamond-like carbon, gallium nitride, gallium arsenide,germanium, Si—Ge alloys, ITO, boron carbide, silicon nitride, alumina,ceria, tin oxide, zinc titanate and plastic.
 9. The method of claim 8,wherein said precursor thin film is annealed at a temperature of250-650° C.
 10. The method of claim 1, wherein said precursor thin filmis annealed at a temperature of 50-850° C.
 11. The method of claim 10,wherein said precursor thin film is annealed in Se atmosphere at atemperature of 450-600° C. for 10 to 60 minutes, and in S atmosphere ata temperature of 350-550° C. for 10 to 60 minutes.
 12. The method ofclaim 1, wherein a thickness of said CIGSS compound thin film of step(4) is 5-5000 nm.
 13. The method of claim 1, wherein said adding saidsolution conditioner thereby stabilizes said clear stable sourcesolutions.